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Power transformer is one of the key equipment of power grid. The quality defects of power transformer are inevitable for the long cycle manufacturing period with complex technology and artificial factors, which will affect the safety and stability operation. It has great significance to study on the quality risk assessment of power transformer. With the manufacturing supervision information source,...
In recent years, the manufacturing industry of distribution transformer (DT) in China has developed rapidly, and the competition is highly. The quality of the DTs was worried, where even using aluminum winding instead of copper winding in DTs without symbol. During the 13th Five-Year Plan period, the investment of distribution network construction will reach 1.7 trillion RMB, which makes a big market...
Power transformer is one of the key equipment in the power grid. Its quality is directly related to the continuous and stable operation of the power system. It is difficult to evaluate the power transformer quality, because of the complex technology, longtime manufacturing cycle, and high fuzzy information. The quality fuzzy synthetic evaluation method for power transformer based on life cycle theory...
In this work we investigate properties of ultra-narrow photoluminescence lines originating from recombination of excitons trapped by short-range potential fluctuations, caused by alloy disorder in GaAs/GaNAs core/shell nanowires. From power-dependent photoluminescence measurements we show that the emission behavior is consistent with biexciton-exciton cascade recombination in quantum dots. We also...
Semiconductor quantum dot (QD) structures are considered as promising building block for spintronic applications with the advantage of prolonged spin relaxation time owing to 0D character of confined carriers or excitons. However, feasible application is haunted by severe spin injection loss from its adjacent barrier layers and its mechanism is still not fully understood. Here, we show that exciton...
In this paper we review our recent results on optical properties of coaxial nanowires (NWs) based on dilute nitride alloys, such as GaAsN and GaNP. We show that these structures have a high structural and optical quality, and can potentially be used as polarized nano-scale light sources that emit linearly polarized light with the polarization direction perpendicular to the wire axis even in zinc blende...
Proper determination of light use efficiency (LUE) is a prerequisite for LUE models to simulate gross primary productivity (GPP). This study was devoted to apply the photochemical reflectance index (PRI) to accurately track LUE variations for a sub-tropical coniferous forest using tower-based PRI and GPP measurements. To improve the ability of PRI to track LUE, a simple two-leaf approach is used to...
Differential flip-flop designs for high-speed operations are evaluated for single-event (SE) effects using circuit-level simulations. Results show input dependent SE performance of some differential flip-flop designs. Radiation hardenings by layout optimization for all differential flip-flops and by circuit design for SSTC are discussed.
In this paper, we present a novel hybrid UAV, U-Lion, which has autonomous VTOL and cruise flying capabilities. The reconfigurable wings are designed so that the structure of U-Lion is aerodynamically efficient in both flying modes. Vectoring thrust and the multiple control surfaces tail are implemented to increase the controllability for better maneuverability and stronger rejection to wind gust...
Aggressive maneuvers for micro unmanned aerial vehicle (MAV) require short settling time for attitude reference tracking and small overshoot for stabilization, which leads to the implementation of composite nonlinear feedback (CNF) control method. In this paper, an MAV platform is customized with all of the sub-systems designed to be small in size factor and simplified with their functionality. A...
Photosynthesis in vegetation is arguably the most important and variable part of the terrestrial carbon cycle. In terrestrial biospheric models, the photosynthesis rate of plant leaves is generally simulated based on the maximum carboxylation rate at an optimum temperature (often 25°C), which is often denoted as Vcmax25. In regional and global photosynthesis modeling, Vcmax25 is usually prescribed...
This paper proposes a new approach for detection and classification of power quality (PQ) disturbances in time domain. Most research in this field employs frequency domain analysis tools to analyse the features of PQ disturbances, such as Fourier transform and wavelet transform. However, the transient and steady-state characteristics of PQ disturbances are originally reflected on the waveforms of...
In this paper, we introduced an online path planning method which is able to be implemented on micro rotorcrafts with limited payload and computational power. The method enables automatic flight of such vehicles in GPS-denied and obstacle-strewn environments by adopting efficient trajectory generation algorithms. A series of two point boundary value problem (TPBVP) is solved analytically to formulate...
This manuscript describes a UAV implemented with vision and laser based localization algorithm to track and land on a moving platform. Specifically, a pre-designed marker is installed on the moving platform and a downward facing monocular camera is mounted on the UAV for pose estimation. For a robust and precise UAV height estimation, a LiDAR scanning range finder is utilized to determine accurate...
This paper presents the autonomous control of a fully customized quadrotor MAV in GPS-denied environments based on onboard visual odometry. To achieve the best integration and efficiency, key modules of the MAV hardware system have been investigated and optimized iteratively, inclusive of mechanical frame, propulsion system, flight controller and the visual sensor. An optical-flow module is developed...
This paper presents a systematic design approach for an unconventional UAV, J-Lion. J-Lion is a UAV featured by its hybrid flight capability in both VTOL and fixed-wing modes. Besides, a morphing wing concept is also realized by the extensible wing design. To reduce the development cycle, our approach takes into account the common factors systematically in the conceptual design phase, including overall...
In this paper, we present a fully autonomous quadrotor for indoor exploration. The quadrotor is fully customized and capable of localization, mapping, planning and flying in unknown indoor environment with all real-time computations performed onboard. Two laser scanners are equipped to determine the 3D position of the quadrotor. The position measurements are further fused with Inertial Measurement...
This paper presents a design and implementation of an unmanned aerial vehicle (UAV) for outdoor firefighting application. The proposed UAV firefighting system consists of a self-designed quadcopter as platform, a transmission system to collect and release water, a real time kinematic (RTK) based navigation system and a mission control system to monitor and coordinate the UAV. In our proposed autonomous...
Cargo transportation between moving platforms is one of the most meaningful potential applications of UAVs. However, to fully autonomously transport the cargos, the UAV is required to have high position precision and high intelligence to tackle all the emergencies, on which the technology is not mature yet. In this article, we present a quadrotor system targeting at fully autonomous cargo transportation...
Majority of today's fixed-pitch, electric-power quadrotors have short flight endurance (< 1 hour) which greatly limits their applications. This paper presents a design methodology for the construction of a long-endurance quadrotor using variable-pitch rotors and a gasoline-engine. The methodology consists of three aspects. Firstly, the rotor blades and gasoline engine are selected as a pair, so...
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